To　explore　the　modification　of　rheological　behavior　of　fresh　cement　paste　by　in　situ　polymerization,　the　rheological　properties　of　fresh　in　situ　polymerization　modified　cement　(IPMC)　pastes　with　various　acrylamide　(AM)　monomer　dosages　and　resting　time　were　investigated　by　rheology　test　in　this　paper.　The　interaction　mechanism　between　inorganic-organic　components　of　IPMC　paste　and　its　influence　on　rheology　are　also　discussed.　The　results　revealed　that　the　yield　stress　and　plastic　viscosity　of　fresh　IPMC　paste　decreased　as　the　AM　dosage　increased,　and　rose　rapidly　with　the　resting　time　when　the　AM　dosage　was　more　than　5%.　The　time-dependent　rheological　properties　of　IPMC　paste　were　associated　with　various　periods　of　AM　polymerization　reaction.　This　paper　also　found　that　the　dispersing　effect　produced　by　the　AM　adsorption　and　the　flocculating　effect　generated　from　the　polyacrylamide　(PAM)　microgels　bridging　would　jointly　impact　the　structural　buildup　of　IPMC　paste;　the　former　improved　the　rheological　properties　and　fluidity,　while　the　latter　acted　contrary.　Our　results　provide　the　underlying　insights　needed　to　guide　the　dynamic　regulation　of　rheological　properties　of　cement-based　materials　by　in　situ　polymerization　modification.　　©　2023　American　Society　of　Civil　Engineers.